BD91361MUV Datasheet, PDF (14/18 Pages) Rohm – Output 2A More High-efficiency Step-down Switching Regulator with Built-in Power MOS FET

BD91361MUV
Technical Note
5. Determination of output voltage
The output voltage VOUT is determined by the equation (6):
VOUT=(R2/R1+1)×VADJ・・・(6) VADJ: Voltage at ADJ terminal (0.8V Typ.)
With R1 and R2 adjusted, the output voltage may be determined as required.
Adjustable output voltage range : 0.8V～3.3V
6
SW
1
ADJ
L
Co
Output
R2
R1
Fig.36 Determination of output voltage
Use 1 kΩ～100 kΩ resistor for R1.
If a resistor of the resistance higher than 100 kΩ is used, check the assembled set carefully for ripple voltage etc.
3.7
The lower limit of input voltage depends on the output voltage.
3.5
Basically, it is recommended to use in the condition :
VCCmin = VOUT+1.2V.
Fig.37. shows the necessary output current value at the lower limit
3.3
of input voltage. (DCR of inductor : 20mΩ)
This data is the characteristic value, so it’ doesn’t guarantee the
3.1
operation range,
2.9
Vo=2.5V
Vo=2.0V
Vo=1.8V
●BD91361MUV Cautions on PC board layout
2.7
0
1
2
3
OUTPUT CURRENT : IOUT[A]
Fig.37 minimum input voltage in each output voltage
Fig.38 Layout diagram
①Lay out the input ceramic capacitor CIN closer to the pins PVCC and PGND, and the output capacitor Co closer to
the pin PGND.
②Lay out CITH and RITH between the pins ITH and GND as neat as possible with least necessary wiring.
※VQFN020V4040 (BD91361MUV) has thermal PAD on the reverse of the package.
The package thermal performance may be enhanced by bonding the PAD to GND plane which take a large area of PCB.
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14/17
2010.06 - Rev.A